Algorithm of getting free IP address - php

Question

I use yii2. And I need to find IP which is not used (is not in database) by method getFreeIPAddress. I have class like this:
class Radreply extends ActiveRecord {
const ATTRIBUTE_DEFAULT_IP_ADDRESS = 'Framed-IP-Address';
const IP_ADDRESS_MAX = '10.255.255.255'; // max value for IP
const IP_ADDRESS_MIN = '10.0.0.11'; // min value for IP
public function getIntegerIP(){ // converts IP from string to integer format
return ip2long($this->value);
}
public static function getFreeIPAddress(){
$records = self::findAll(['attribute'=>self::ATTRIBUTE_DEFAULT_IP_ADDRESS]); // get all record which contain IP address
$existIPs = ArrayHelper::getColumn($records,'integerIP'); // get array of IP which is converted to integer by method getIntegerIP
for ($integerIP = ip2long(self::IP_ADDRESS_MIN); $integerIP<=ip2long(self::IP_ADDRESS_MAX); $integerIP++){
// increasing one by one IP address in integer format from value IP_ADDRESS_MIN to value IP_ADDRESS_MAX
if (!in_array($integerIP, $existIPs)){
$stringIP = long2ip($integerIP);
$arrayDigits = explode('.', $stringIP);
$lastDigit = array_pop($arrayDigits);
if ($lastDigit!='0'){ // check if last digit of IP is not 0
return $stringIP;
}
}
}
return '';
}
}
Method getFreeIPAddress works find, but in db there are a lot of records with IP and increasing one by one IP and checking if this IP exist in db is very long way. How I can optimize this algorithm? Is there faster way to get unused IP?

Answer 1

I think, I've found better solution without extra table in database
class Radreply extends ActiveRecord {
const ATTRIBUTE_DEFAULT_IP_ADDRESS = 'Framed-IP-Address';
const IP_ADDRESS_MAX = '10.255.255.255'; // max value for IP
const IP_ADDRESS_MIN = '10.0.0.11'; // min value for IP
public function getIntegerIP(){ // converts IP from string to integer format
return ip2long($this->value);
}
public static function getFreeIPAddress(){
$records = self::findAll(['attribute'=>self::ATTRIBUTE_DEFAULT_IP_ADDRESS]); // gets all record which contain IP address
$existIPs = ArrayHelper::getColumn($records,'integerIP'); // gets array of IP which is converted to integer by method getIntegerIP
$intIpAddressMin = ip2long(self::IP_ADDRESS_MIN); // gets min IP in integer format
$endRange = empty($existIPs) ? $intIpAddressMin : max($existIPs); // checks if at least one IP is used
$availableIPs = range( $intIpAddressMin, $endRange + 2); // generates array with available IP addresses (+2 because next address can be with last digit 0)
$missingIPs = array_diff($availableIPs,$existIPs); // removes all used IP
foreach ($missingIPs as $value){
$lastDigit = $value % 256;
if ($lastDigit != 0){
return long2ip($value);
}
}
return '';
}
}

Answer 2

bool in_array ( mixed $needle , array $haystack [, bool $strict = FALSE ] )
In my opinion，you can set strict true .
my php code with strict = false
<?php
$y="1800";
$x = array();
for($j=0;$j<50000;$j++){
$x[]= "{$j}";
}
for($i=0;$i<30000;$i++){
if(in_array($y,$x)){
continue;
}
}
time php test.php
real 0m4.418s
user 0m4.404s
sys 0m0.012s
when strict is true
for($i=0;$i<30000;$i++){
if(in_array($y,$x ,true)){
continue;
}
}
time php test.php
real 0m1.548s
user 0m1.540s
sys 0m0.004s
what‘s more ,if you can get the used ip with ascending order . you can get the o(m+n) time complexity,which m is the length of all ip you should try , n is the length of all ip in db with merge algorithm .
if you can get the used ip with ascending order
in Pseudocode .
tmpIp = minIp;
while(temIp <= maxIp){
if( dbIsEmpty){
break;
}
dbIp =getNextFromDb();
while(temIp < dbIp){
printf temIp ;
temIp ++;
}
temIp ++;
}
while(temIp <= maxIp){
printf temIp ;
temIp++;
}
here is my php code, where i repalce echo ip by $count++;
In this demo there is about 80000 ip with type of long
<?php
function mergeSort( $result){
$minIp = ip2long('10.0.0.11') ;
$maxIp = ip2long('10.255.255.255');
$count =0;
$tmpIp = $minIp;
while($temIp <= $maxIp){
if( empty($result)){
break ;
}
$tmp = array_pop($result);
$dbIp =$tmp['ip'];
while($temIp < $dbIp){
// echo temIp ;
// i repalce it by count ++ , i don't want it
//full my teminal .
$count ++;
$temIp ++;
}
$temIp ++;
}
while($temIp <= $maxIp){
//echo $temIp ; replace by $count++
$count ++;
$temIp++;
}
return $count -1;
}
$servername = "localhost";
$username = "root";
$password = "aaaaa";
$dbname = "IP";
$conn = new PDO('mysql:host=' . $servername . ';dbname=' . $dbname , $username, $password);
$conn->setAttribute(PDO::ATTR_AUTOCOMMIT , true);
$stmt = $conn->prepare("select * from ipTable order by ip desc");
$stmt->execute();
$result = $stmt->fetchAll();
$count = mergeSort($result);
echo $count ;
?>
it take about 10s ;
time php test.php
184460881
real 0m10.626s
user 0m10.416s
sys 0m0.168s